Method of making disintegrating bodies for use as practice ammunition



6, 1969 R. GERMERSHAUSEN 3,

METHOD OF MAKING DISINTEGRATING BODIES FOR USE AS muons AMMUNITION FiledMarch 10, 1967 lnventoh RaLmunJ er-mem'lmus n "United States Patent3,463,047 METHOD OF MAKING DISINTEGRATING BODIES FOR USE AS PRACTICEAMMUNITION Raimund Germershausen, Dusseldorf, Germany, assignor to FirmaRheinmetall G.m.b.H., Dusseldorf, Germany Filed Mar. 10, 1967, Ser. No.622,356 Claims priority, appliclgtigg Germany, Mar. 11, 1966,

US. Cl. 86-23 1 Claim ABSTRACT OF THE DISCLOSURE A method of makingpractice rounds of ammunition in which equal parts by weight of ironpowder Whose particles have a greatly cleft surface and iron powderwhose particles have a smooth spherical surface are mixed with alubricant for example graphite, wax or synthetic resin products andcompacted and then placed in a casing.

The invention relates to a method of making disintegrating bodies foruse as practice ammunition. The bodies consist of a single-part ormultipart molding of a metal powder mixture enclosed in a projectilecasing of a plastics material. To the metal powder is added a lubricantwhich stops caking of the molding on disintegration of the projectileafter the latter has left the muzzle of the weapon from which the roundof ammunition was fired.

The requirements to be met by a successful practice round are veryexacting. Thus, the round, especially if it is to be fired from anautomatic weapon, must be equal to the high mechanical stresses whichoccur during feeding, loading and on firing on the one hand and on theother hand, the round must so disintegrate immediately after leaving themuzzle that it is not able to do damage beyond a certain distance fromthe muzzle. It is important that the external shape and the weight ofsuch a practice round shall resemble closely those of a live round. Insuch case, weights per unit of volume of about 6.5 g./cc. are requiredof the disintegrating body of a practice round for automatic weapons andthese densities can be produced from loose material only by means ofheavy metal powder which are costly. Thus, as is known, the casing ofthe round, which is made of cardboard, thin sheet metal or a plasticsmaterial is filled with a powdered heavy metal, for example lead powder,to which there is added graphite, talc or the like which is ostensiblyintended to prevent the metal powder particles caking together ondisintegration of the round.

As agglomeration of the meta 1 powder cannot be achieved satisfactorilyby such additions alone, a casing filled with such a charge does nothave adequate mechanical strength.

Another method is also known in which the internal cohesion of a moldingconsisting of iron powder is reduced. The metal powder is first formedinto moldings under an applied pressure sufficient to secure a requireddensity, after which the coherence of the powder particles in themoldings is so reduced by a mechanical or chemical action, whileretaining the shape of the moldings, that the moldings are able todisperse in fine powder after the round leaves the muzzle.

The mechanical or chemical aftertreatment for the purpose of reducingthe cohesion is not only costly, but also is difiicult to reproducereliably.

It is thus an object of the present invention to avoid these drawbacksand produce moldings of metal powder for disintegrating rounds whichcorrespond in form and weight to a normal live round, which have thenecessary mechanical strength and which disintegrate into minuteparticles, lacking all power of penetration, shortly after leaving themuzzle. Moreover, the rounds must not expose the weapon to unnecessarywear or any damage.

The present invention is based on the surprising discovery that thedisintegration properties of iron powder moldings can be considerablyimproved by a suitable choice of the starting materials as regards thesize and nature of the surface of the particles of iron and by addingspecial lubricants. Such improvement is obtained without the strengthrequired for handling during the manufacture of the round and towithstand the stresses during the feeding and loading process in theweapon being impaired at the same time.

According to the present invention the procedure which is followed inmaking moldings for disintegrating practice rounds is that iron powderwhose particles have a greatly cleft or roughened surface and ironpowder whose particles have a smooth spherical surface are subjected, inapproximately equal parts by weight, to a mixing treatment with theaddition of a lubricant, after which the pourable mixed material iscompacted under a load per unit of area of from about 6.5 to about 8.0tons/sq. cm. into a single-part or multipart molding conforming to theinternal shape of the casing.

The interengagement of the cleft or roughened and smooth iron particlesdoes not have a major eifect on the strength of the molding. Theaddition of the lubricant with its adhesive effect is the main factoraffecting the strength.

Another advantage of the lubricant is that it causes the iron particlesto slide over one another with reduced friction and interengagementduring the compacting operation.

The lubricant itself may consist of a mixture of stearic acid and finelyground Phosphor bronze. The stearic acid is first melted and thePhosphor bronze dust is then introduced into the melt while stirring.This mixture is thereafter cooled while being stirred vigorously. Thesolidified suspension is then ground until the particle size is amultiple of that of the Phosphor bronze dust introduced. The effect ofthe lubricant can be further improved by adding paraflin oil.

As a result of the bonding of the iron patricles by the lubricant, thereis obtained in particular, good strength at fairly low compactingpressures and, at the same time, reliable reduction of the round to dustin front of the muzzle.

Although it has been found by an extensive series of tests that amixture of stearic acid and Phosphor bronze is outstandingly suitable asa lubricant and is one which can be mixed very well with the ironpowder, other lubricants may be used, among which are, for example,graphits, waxes or synthetic resin products.

By way of example only, methods embodying the invention of producingpractice rounds will now be described in greater detail with referenceto the accompanying drawing which is a section through the round.

The first method to be described employs the following constituents:

(a) Iron powder whose particles have greatly cleft or roughened surfaceand a tendency for interengagement, in which the particle sizes aredivided as follows.

Percent by weight:

stearic acid and 84 percent by weight of Phosphor bronze powder ofparticle size about 50 By homogenization of the stearic acid melt andsubsequent grinding, a mixture is produced the particle size of which isbelow 460g.

The proportion by weight of the lubricant in the total weight of adisintegrating body is 3 to 8 percent by weight.

The constituents are mixed together in a mixer with the addition of 2 tocc. of parafiin oil per kilogram of the quantity used until the powderhas been completely mixed. The loose material obtained in this way isthen compacted at a loading per unit of area of 6.5 to 8 tons/ sq. cm.to produce a body whose shape approximates to that of a projectile.

In a second method the following particularly satisfactory compositionis used:

50 percent by weight of an iron powder having particles with smoothspherical iron powder, a particle size of about 250, and a knockingweight of 4.15 g./cc.

45 percent by weight of iron powder whose particles have a greatly cleftor roughened surface with a particle size below 150,11. and a knockingweight of 2.95 g./cc.

5 percent by weight of lubricant 5 cc./kg. of paraffin oil 7,500 kg./sq.cm. pressure of compression.

The constituents are mixed together as before and then compacted toproduce a projectile-shaped body.

The drawing shows a disintegrating practice ammunition round whichconsists essentially of a casing 1 of a plastic material, a long-shankedbase part 2 and a reinforcing element 3 arranged in the casing in thezone of the rotating or driving band. Before the reinforcing element isinserted, the disintegrating bodies 4 and 5 consisting respectively of amoulding tapering to a point and a cylindrical moulding into the emptyprojectile casing 1 are inserted into the casing, after which, once theelement 3 has been inserted, the shank of the projectile base 2, whichis likewise filled with a disintegrating body 6, is inserted in theprojectile casing 1.

Of course, the arrangement may also be such that,

4 with the reinforcing element 3 eliminated, a disintegrating body whichis continuous from base to tip is employed as the core of the round.

I claim:

1. A method of preparing a disintegrating practice ammunition roundhaving an outer plastic casing, comprismg:

mixing approximately equal parts of iron powder particles having greatlycleft roughened surfaces with iron powder particles having smoothspherical surfaces,

preparing a lubricant by mixing stearic acid and finely ground Phosphorbronze powder to form mixed particles of a multiple size of the Phosphorbronze particles,

mixingsaid iron particles with said mixed lubricant particles,

pouring the last mentioned mixed materials into a mold adapted to theinternal shape of said plastic casing,

pressing said material mixture within said mold under a pressure of 6.5to 8.0 tons per sq. cm. to form a compact body therefrom,

removing said compact body from said mold, and

inserting said compact body within said plastic casing to form saidammunition round.

References Cited UNITED STATES PATENTS 3,216,358 11/1965 Findeisenl02-92.7

FOREIGN PATENTS 625, 64 7/1946 Great Britain. 718,252 11/1954- GreatBritain.

ROBERT F. WHITE, Primary Examiner J. R. HALL, Assistant Examiner US. Cl.X.R.

